Much research, efforts and time have been expended to produce fuel compositions for internal combustion engines which show significant decreases upon combustion of toxic exhaust gases or vapors, particulate, smoke, and the like without sacrifice of engine performance or efficiency. It is currently known by those skilled in the art that the introduction of oxygenates into fossil fuels contributes to better burning and the reduction of toxic exhaust emission. Ethanol is one such oxygenate which, when used with gasoline for instance, reduces toxic emissions.
A problem, however is that ethanol attracts water and will separate from gasoline in the presence of certain amounts of water condensation. Another problem is that ethanol is generally denatured using methanol, which exacerbates the problem of water separation and produces unacceptable solvency levels, such that ethanol/methanol/gasoline mixtures cannot be transported through existing pipelines. Another problem associated with using ethanol as an oxygenate is that ethanol, as well as methanol and other water-soluble alcohols, will not mix at all with less refined fossil fuels, such as diesel fuel or other distillate fuels like kerosene.
Conventional diesels, derived from crude petroleum, are used in a variety of applications, such as in transportation, power generation and the like.
Due to non-renewable nature of hydrocarbon fuels, considerable attention has been focused on development of alternate fuel sources. Oxygenated fuels containing ethanol or water have now been considered as the potential hybrid fuels and have gained the technical acceptance. The favourable economics of ethanol production and its increased availability combined with the beneficial effect on emissions has been the main factor behind development of ethanol-diesel blends. Thus, for the purpose of economics, combustion properties and renewal nature, ethanol is widely being used in hybrid diesel formulations which are also called ‘oxydiesel’.
While 5-10% anhydrous ethanol is miscible in diesel at room temp (25° C.), trace amount of water or lower temperature cause immediate separation of the ethanol from the blends. Additionally, at lower temperatures, the ability of blend to tolerate moisture is much less and phase separation results. This separation of ethanol-water from the hydrocarbon body is undesirable as it could cause erratic combustion and severe corrosion in the fuel delivery system. Another major problem of making ethanol-diesel blends is of operational nature. This blend making process is energy intensive and it is very difficult to homogenise the blend.
Emulsion or micro emulsions containing hydrocarbon liquid in the continuous phase and alcohol or water in a dispersed phase have been described in a number of patents. These emulsions need a stabiliser which generally acts like an emulsifier.
A PCT application WO 9907465 by Apace research of Australia described an emulsifier, which is a block co-polymer of styrene or substituted styrene with ethylene oxide. Additionally, a coupler is also necessary which is chemically a block co-polymer of styrene or substituted styrene with other hydrocarbons like butadiene. EP patent 0089147 describes the use of block ethylene oxide-styrene copolymer for emulsifying alcohols in diesel fuel. Another PCT application WO 0031216 describes a ethanol solubilised diesel fuel composition.
PCT application WO 9935215 describes a additive composition also used as a fuel composition comprising water soluble alcohols. A German patent (DE 3525124, 1987) reported an emulsifier for making diesel-ethanol blends. The emulsifier was prepared by reaction of oleic acid with ethoxylated oleylamine.
U.S. Pat. Nos. 6,190,427 and 6,017,369 describe diesel fuel compositions stabilised by a mixture of fatty acid alcohols and a polymeric material. Another U.S. Pat. No. 4,451,265 describes diesel fuel-aqueous alcohol microemulsions based on a dimethylethanol amine surfactant system. A US patent (256206, 1981) describes a surfactant system containing N,N-dimethyl ethanol amine and long chain fatty acid.
Cashew nut shell liquid (CNSL) occurs as a reddish brown viscous liquid in the soft honeycomb structure of the shell of cashewnut, a plantation product obtained from the cashew tree, Anacardium Occidentale L. Native to Brazil, the tree grows in the coastal areas of Asia & Africa. Cashewnut attached to cashew apple is grey colored, kidney shaped and 2.54 cm long. The shell is about 0.3 cm thick, having a soft leathery outer skin and a thin hard inner skin. Between these skins is the honeycomb structure containing the phenolic material popularly called CNSL. Inside the shell is the kernel wrapped in a thin brown skin, known as the testa.
The nut thus consists of the kernel (20-25%), the shell liquid (20-25%) and the testa (2%), the rest being the shell. Natural CNSL, extracted with low boiling petroleum ether, contains about 90% anacardic acid and about 10% cardol. Natural CNSL, on distillation, gives the pale yellow phenolic derivatives, which are a mixture of biodegradable unsaturated m-alkenylphenols, including cardanol. Catalytic hydrogenation of these phenols gives a white waxy material, predominantly rich in tetrahydroanacardol.
CNSL and its derivatives have been known for producing high temperature phenolic resins and friction elements, as exemplified in U.S. Pat. Nos. 4,395,498 and 5,218,038. Friction lining production from CNSL is also reported in U.S. Pat. No. 5,433,774. Likewise, it is also known to form different types of friction materials, mainly for use in brake lining system of automobiles and coating resins from CNSL. U.S. Pat. No. 6,229,054 describes a process for hydroxyalkylation of cardanol with cyclic organic carbonates. CNSL derivatives have also been used for metal extraction, as exemplified in U.S. Pat. No. 4,697,038. In another U.S. Pat. No. 4,352,944, mannich bases of CNSL have been described.
However, the first application of CNSL in making lubricating oil additives was disclosed by us in U.S. Pat. Nos. 5,910,468 and 5,916,850. U.S. Pat. No. 6,339,052 also describes lubricant compositions for internal combustion engines based on additives derived from cashew nut shell liquid.
Ethoxylated alcohols have been used in past as a stabilising emulsifying additives for making stable ethanol-petroleum fuel compositions.
For example, a U.S. Pat. No. 6,080,716 of 2000 describes a surfactant which is made by reaction of aliphatic alcohol with ethylene oxide. The non-ionic ethoxylated surfactant, as stabilising additives are prepared from reaction of aliphatic alcohol with ethylene oxide and are also available commercially e.g., Neodol 91-2.5 from Shell chemicals. Thus, Neodols prepared from reaction of C9 to C11 alcohol with ethylene oxide to give products having average number of ethylene oxide from 2.5 to 10 per mole of alcohol (U.S. Pat. No. 6,183,524 of 2001) have been used as the stabilising additives.